Theoretical Calculations Research Articles

Spectroscopic elucidation, quantum chemical computations (FMO, HOMO–LUMO, MEP, NLO), and biological activity on some novel heterocyclic compounds using 3-substituted-6,8-dimethylchromones

The chemical transformations of substituted chromones 1a–c were examined toward some nucleophiles namely dimedone (R1), 4-hydroxycoumarin (R2) and 4-hydroxy-1-methylquinolin-2(1H)-one (R3). DFT computation at the B3LYP/6-311 G(d,p) level of theory was used to perform the theoretical computations for the produced compounds. HOMO and LUMO analyses were performed to determine the electronic charge distribution and reactivity of the molecules. Molecular electrostatic potential (MEP) surface analysis was utilized to predict the molecule’s reactive sites. Moreover, the studied compounds showed NLO characteristics, where they have first order hyperpolarizability greater than urea. In addition, the GIAO method was used to estimate the 1H-NMR and 13C-NMR chemical shifts; and the findings were compared with experimental values. Testing the generated compounds for antibacterial and anticancer activities revealed varied degrees of inhibitory effect. According to the Lipinski, Veber, and Egen rules, these compounds exhibit physicochemical properties.

Assessment of unidirectional internal solitary wave models in a two-layer fluid system through an improved experimental method

The suitability of unidirectional internal solitary wave (ISW) models in a two-layer fluid system is evaluated using an improved experimental method. A new method for generating internal solitary waves in the laboratory tank is proposed, utilizing a piston-type wave maker in a density stratified two-layer fluid. The prescribed velocities of the pistons are determined by the mean velocities derived from the adjusted High-order Unidirectional (aHOU) model for the upper and lower layers. Experimental conditions encompass a range of wave Reynolds numbers between 1.8×105 and 2.3×105. The repeatability and amplitude control of the proposed wave-making method are verified. The unidirectional models considered in this study encompass the Korteweg–de Vries (KdV), Gardner and aHOU model. Laboratory experiments and theoretical computations have been systematically compared in this study to examine the wave characteristics inherent in typical unidirectional internal solitary wave models. It is found that Reynolds number (Re) and nonlinear parameter (α=|a|/h) serve as suitable criteria for delineating the range of applicability of unidirectional models. According to these criteria, the KdV theory is suitable for ISWs with amplitudes α<0.02 across all Reynolds number cases, while the Gardner model is valid for cases where α<0.02 and Reω>2.2×105, with α<LimG, where LimG represents the non-dimensional limiting amplitude. The aHOU model exhibits the capability to capture fully nonlinear ISWs across all Reynolds numbers considered in this study.

Thermal stability and properties of silicon-germanium nanocrystals

Using first-principles calculations and ensemble theory, we have calculated the ground-state energy and electronic properties of SixGe10−xH16 nanocrystals, and analyzed their stability and properties at finite temperatures. We have determined the numerical correspondence between chemical potential and the proportion of element in SixGe10−xH16. The probability of various structures appearing within SixGe10−xH16 nanocrystals depends on temperature and chemical potential environment. The influence of vibrational free energy, as investigated by theoretical computations, is also summarized. The research results show that vibrational free energy enhances the structure stability by the occupation of Ge atoms and results in a more concentrated distribution of the gap between the highest occupied molecular orbital and the lowest unoccupied molecular orbital.

Tetramethylpyrazine Cocrystals with Cinnamic Acid and Its Derivatives: Crystal Structures, Theoretical Computations, and Sublimation Behavior Studies

Tetramethylpyrazine Cocrystals with Cinnamic Acid and Its Derivatives: Crystal Structures, Theoretical Computations, and Sublimation Behavior Studies

Interfacial Electronic Interactions Promoted Activation for Nitrate Electroreduction to Ammonia over Ag-modified Co3O4.

Electrocatalytic nitrate (NO3-) reduction to ammonia (NRA) offers a promising pathway for ammonia synthesis. The interfacial electronic interactions (IEIs) can regulate the physicochemical capabilities of catalysts in electrochemical applications, while the impact of IEIs on electrocatalytic NRA remains largely unexplored in current literature. In this study, the high-efficiency electrode Ag-modified Co3O4 (Ag1.5Co/CC) is prepared for NRA in neutral media, exhibiting an impressive nitrate conversion rate of 96.86%, ammonia Faradaic efficiency of 96.11%, and ammonia selectivity of ~100%. Notably, the intrinsic activity of Ag1.5Co/CC is ~81 times that of Ag nanoparticles (Ag/CC). Multiple characterizations and theoretical computations confirm the presence of IEIs between Ag and Co3O4, which stabilize the CoO6 octahedrons within Co3O4 and significantly promote the adsorption of reactants (NO3-) as well as intermediates (NO2- and NO), while suppressing the Heyrovsky step, thereby improving nitrate electroreduction efficiency. Furthermore, our findings reveal a synergistic effect between different active sites that enables tandem catalysis for NRA: NO3- reduction to NO2- predominantly occurs at Ag sites while NO2- tends to hydrogenate to ammonia at Co sites. This study offers valuable insights for the development of high-performance NRA electrocatalysts.

Reduction of 2-phenyl-3a,4,7,7a-tetrahydro-1H-isoindole-1,3(2H)-dione with NaBH4: Investigation of exo-selectivity and reaction mechanism via theoretical computations

The reaction of the bicyclic imide with NaBH4 afforded acylaminocarbinol and carboxamide derivatives. The exact configuration of acylaminocarbinol 7 was determined by X-ray crystal analysis. Theoretical studies were carried out to explain the mechanism of the exo-selectivity observed in the first step of the reduction reaction and the formation of the secondary product in the second step. According to the obtained findings, i) in the first step of the reaction, the exo-path is kinetically more favorable, and ii) an alternative mechanism has been proposed instead of the mechanism proposed in the literature. The canonical forms of the amide group in the lactam ring were found to make an important contribution to the mechanism. iii) The amount of products formed in the reduction reaction depends on the reaction conditions.

Conformational stabilisation of a 2-pyridyl imide by n→π* interaction in solid state

ABSTRACT In recent studies, n→π* interactions featuring nucleophilic pyridine have been investigated using Fourier transform microwave spectroscopy and high-level theoretical computations. Examples of n→π* of this type in the solid state, however, are limited. The norbornene-based 2-pyridyl imide 1 is a compound that can adopt two conformers, in which the pyridyl nitrogen is either syn or anti to the norbornane bridge. It would be expected that the syn conformation of imide 1 would be more favourable, as indicated in a previous computational study. Here, tandem crystallographic and additional computational studies provide evidence that the otherwise unfavourable anti conformer of imide 1 becomes favoured upon stabilisation by an n→π* interaction in the solid state.

Mechanical properties of high-entropy carbides prepared by high-pressure sintering: Role of carbon stoichiometry

The scarcity of carbon in high-entropy carbides is widely recognized to significantly affect their fabrication and performance. However, achieving both high hardness and plasticity in these carbides remains a formidable challenge. This study investigates the impact of carbon vacancies on the phase structure and mechanical properties of high-entropy carbides, particularly (Hf0.25Zr0.25Nb0.25Ta0.25)Cx (x = 1, 0.8, 0.6, or 0.5), utilizing density functional theory calculations and experimental analysis. Theoretical computations indicate a rock-salt structure for the carbides, with reduced cell parameters as carbon vacancies increase. Notably, carbides with lower carbon content exhibit softer characteristics, as evidenced by Pugh's ratio. Experimental fabrication and testing reveal a decrease in Vickers hardness with decreasing carbon content, attributed to changes in bonding types. Certain compositions, particularly (Hf0.25Zr0.25Nb0.25Ta0.25)C0.6 and (Hf0.25Zr0.25Nb0.25Ta0.25)C0.5, display plastic behavior alongside high hardness, offering promising avenues for future research and design of high-entropy ceramics.

A spring-mass-damper model based on separated phase flow mode for pulsating heat pipe with adjustive-structured channels

Pulsating heat pipe (PHP) is a kind of efficient passive phase-change cooling device. The pulsating behaviors of the two-phase flow inside PHP significantly affect the heat transfer performance for PHP, the investigation of which will greatly contribute to the optimal design of PHP for electronic heat dissipation in small space. In the present work, the heat transfer performance of PHP is optimized via structure analysis and modeling calculation. A new “spring-mass-damper” model in terms of separated phase flow mode is established, where the frictional pressure loss of the real two-phase flow pattern − slug flow in PHP is considered. Besides, a prototype of PHP with adjustive-structured channel (ASCPHP) is proposed. The heat transfer performance of ASCPHP is evaluated with the newly established model. With theoretical computation method, the frequency of ASCPHP the superiority of ASPHP is also confirmed by comparison with other types of PHPs.

Mott interactions driven insulating behaviour in Ruthenium based double perovskites: A2SmRuO6 (A = Ba & Sr)

Double perovskites (DP’s) are important for understanding the diverse physical properties arising from strongly correlated interactions. According to experimental observations, the DP’s A2SmRuO6 (A = Ba & Sr) are insulators; however, first-principles calculations using GGA approximations show that they are metallic. We observed a band gap (Eg) opening of 1.3 eV for Ba2SmRuO6 (BSRO) and 1.4 eV for Sr2SmRuO6 (SSRO) upon the insertion of Hubbard parameter (U) in the theoretical computations for accounting the electron-electron interactions. Further investigations using core-level spectroscopy reveal Eg of 1.05 eV for BSRO and 0.85 eV for SSRO. Furthermore, the calculations for Δ (charge transfer energy), U (coulomb repulsion energy), and W (bandwidth) from the combined spectra show U < Δ and U/W > 1.15, which confirms these compounds be classified as Mott-Hubbard insulators. These results expand our understanding of the strongly correlated compounds around the Fermi level, which might have applications in optoelectronics.

A novel dual swirling air curtain dust-control system: Design and similar experiment

The excessive concentration of dust in fully-mechanized excavation face (FEF) poses a serious risk to the health and safety of workers. This paper proposes a novel dual swirling air curtain (DSAC) dust-control system and conducts similar experiments to evaluate its effectiveness. Firstly, the theory of annular swirling jet and the dust-control mechanism of DSAC are elaborated upon. The subsequent section presents a comprehensive description of the proposed DSAC, outlining its design and the theoretical computations involved. Thereafter, the formation and attenuation of the air curtain, as well as the dust diffusion patterns with and without the DSAC system, are investigated using a similar experimental platform. The results showed that the DSAC can produce a clockwise rotating swirling air curtain. Furthermore, the utilization of the DSAC can effectively mitigate dust concentration on the experimental platform and suppress dust diffusion.

Single‐Atom Catalyst Induced Amorphous Li2O2 Layer Enduring Lithium–Oxygen Batteries with High Capacity

AbstractAprotic lithium–oxygen batteries (LOBs) may deliver exceptionally high energy density but struggle to attain rapid reversibility and substantial capacity simultaneously, due to typical surface or solution‐formed insulating solid Li2O2. Tuning the structure of Li2O2 to create a large‐area amorphous layer on the cathode is predicted to overcome the multiperformance limitations. Here, an isolated nickel single atom to nitrogen‐doped graphene as a cathode catalyst (Ni─NG SAC) for LOBs is presented via a green click‐trapping strategy. Derived from the maximized exposure of atomic active sites of the cathode, the formation/decomposition mechanisms of Li2O2 are tailored, and a large area of thin Li2O2 amorphous film is achieved. The structure and functions of Ni─NG SAC are explored by theoretical computation and synchrotron radiational investigation. Consequently, the abundant Ni─N4 sites enhance redox kinetics and stand out to deliver an impressive specific discharge/charge capacity of 24 248/17 656 mAh g−1 at 200 mA g−1, together with a long cycle life of over 500 cycles. This study contributes helpful insights to achieve high‐capacity LOBs with long lifespans, by constructing unique single‐atom catalysts to optimize the formation of amorphous discharge Li2O2 products.

Disulfide bonded polyimide cathode of rechargeable magnesium batteries: Improved capacity via reversible break/formation of disulfide and sulfur-oxygen bonds

Rechargeable magnesium batteries are a potential selection for large-scale energy storage technologies, but development of cathode materials is the major difficulty at present. Organic polyimides are promising magnesium battery cathodes with the open and amorphous frameworks as well as enhanced charge delocalization. However, only two carbonyls are redox-active out of four for each imide unit, which largely limits the capacity. Herein, a new polyimide containing disulfide bond is fabricated and studied as cathode for rechargeable magnesium batteries. This polyimide shows a high capacity beyond the traditional two-electron principle. A mechanism study demonstrates that carbonyl enolization and disulfide bond break/formation occur in the redox process, leading to formation/break of sulfur-oxygen bond. This sulfur-oxygen bond enhances enolization and electron delocalization, resulting in an improved capacity. Further theoretical computation indicates a charge transfer within this sulfur-oxygen bond. The two-electron reduction state exhibits quite low HOMO and LUMO energy levels, which makes the disulfide bonded polyimide have a higher tendency to accept more electrons and a higher oxidation stability after reduction.

Polynuclear Cobalt Cluster-Based Coordination Polymers for Efficient Nitrate-to-Ammonia Electroreduction.

The electrocatalytic nitrate reduction reaction (NITRR) holds great promise for purifying wastewater and producing valuable ammonia (NH3). However, the lack of efficient electrocatalysts has impeded the achievement of highly selective NH3 synthesis from the NITRR. In this study, we report the design and synthesis of two polynuclear Co-cluster-based coordination polymers, {[Co2(TCPPDA)(H2O)5]·(H2O)9(DMF)} and {Co1.5(TCPPDA)[(CH3)2NH2]·(H2O)6(DMF)2} (namely, NJUZ-2 and NJUZ-3), which possess distinct coordination motifs with well-defined porosity, high-density catalytic sites, accessible mass transfer channels, and nanoconfined chemical environments. Benefitting from their intriguing multicore metal-organic coordination framework structures, NJUZ-2 and NJUZ-3 exhibit remarkable catalytic activities for the NITRR. At a potential of -0.8 V (vs. RHE) in an H-type cell, they achieve an optimal Faradaic efficiency of approximately 98.5% and high long-term durability for selective NH3 production. Furthermore, the electrocatalytic performance is well maintained even under strongly acidic conditions. When operated under an industrially relevant current density of 469.9 mA cm-2 in a flow cell, a high NH3 yield rate of up to 3370.6 mmol h-1 g-1cat. was observed at -0.5 V (vs. RHE), which is 20.1-fold higher than that obtained in H-type cells under the same conditions. Extensive experimental analyses, in combination with theoretical computations, reveal that the great enhancement of the NITRR activity is attributed to the preferential adsorption of NO3- and the reduction in energy input required for the hydrogenation of *NO3 and *NO2 intermediates.

Theoretical and experimental investigations on structural, electronic and biological properties of novel carbazate containing furaldehyde based imines

A convenient and facile synthesis of tert‑butyl (E)-2-(furan-2-ylmethylene) hydrazine-1-carboxylate (a) and ethyl (E)-2-(furan-2-ylmethylene) hydrazine-1-carboxylate (b) were accomplished by refluxing t‑butyl/ethyl carbazate with a furaldehyde in solvent ethanol. The interactions between and within two synthesised imine compounds were characterised and identified by the utilisation of spectroscopic techniques in conjunction with X-ray crystallography and theoretical computations. Compound a crystallises in orthorhombic crystal system with Pbca space group, while as compound b crystalizes in monoclinic crystal systems with space groups Cc. The presence of CH…π stacking and π…π stacking interactions are distinguishing characteristic of crystal packing in both target compounds. Their solid-state behaviour was also studied using Hirshfeld surfaces. Crystal packing motifs were investigated with the aid of Hirshfeld surface fingerprint plots. Furthermore, investigations related to calculations of the molecular electrostatic potential and frontier molecular orbital (highest occupied-lowest unoccupied) were carried out for the optimised structure. Finally, Hormone-sensitive lipase (HSL) (PDB-ID 6KEU) protein was used to conduct molecular docking investigations of compound a and b.

MERA: Meta-Learning Based Runtime Adaptation for Industrial Wireless Sensor-Actuator Networks

IEEE 802.15.4-based industrial wireless sensor-actuator networks (WSANs) have been widely deployed to connect sensors, actuators, and controllers in industrial facilities. Configuring an industrial WSAN to meet the application-specified quality of service (QoS) requirements is a complex process, which involves theoretical computation, simulation, and field testing, among other tasks. Since industrial wireless networks become increasingly hierarchical, heterogeneous, and complex, many research efforts have been made to apply wireless simulations and advanced machine learning techniques for network configuration. Unfortunately, our study shows that the network configuration model generated by the state-of-the-art method decays quickly over time. To address this issue, we develop a ME ta-learning based R untime A daptation (MERA) method that efficiently adapts network configuration models for industrial WSANs at runtime. Under MERA, the parameters of the network configuration model are explicitly trained such that a small number of optimization steps with only a few new measurements will produce good generalization performance after the network condition changes. We also develop a data sampling method to reduce the measurements required by MERA at runtime without sacrificing its performance. Experimental results show that MERA achieves higher prediction accuracy with less physical measurements, less computation time, and longer adaptation intervals compared to a state-of-the-art baseline.

Unraveling the multilayer solid-electrolyte interphase in lithium batteries through depth-sensitive plasmon-enhanced Raman spectroscopy: A theoretical and experimental study

The solid-electrolyte interphase (SEI) plays a crucial role in determining the lithium deposition/dissolution behaviors, thus influencing the reversible operation of Li metal batteries renowned for their ultrahigh specific capacity. Recently, we developed a depth-sensitive plasmon-enhanced Raman spectroscopy (DS-PERS) method enabling the in situ and nondestructive characterization of the nanostructure and chemistry of SEI through synergistic plasmonic structures. However, a lack of comprehensive elucidation of the enhancement mechanisms has impeded a detailed understanding of the depth-resolved signal contributions. In this study, we integrate theoretical computations with experimental methodologies to systematically unravel the working principles of the synergistic plasmonic structures, demonstrating that hot spots can effectively detect Raman signals at key locations across various stages of SEI layer evolution. Following Li deposition, the hot spots transfer from the Cu interfaces to the Li interfaces. With the thickening of the deposited Li, the localized surface plasmon resonance of Cu is gradually shielded, leading to the disappearance of hot spots originated from Li-Li coupling. Subsequently, we propose the utilization of Cu@Li-multilayer shell-isolated nanoparticles to compensate and introduce new hot spots, thereby enhancing the depth sensitivity. Our work provides theoretical insights essential for achieving precise depth-resolved PERS characterization.

New Eco-Friendly Surfactant Corrosion Inhibitors Derived from Polyethylene Glycol: Surface Activity, Gravimetric, Electrochemical, Theoretical Quantum Computation, and Simulation Analysis

New Eco-Friendly Surfactant Corrosion Inhibitors Derived from Polyethylene Glycol: Surface Activity, Gravimetric, Electrochemical, Theoretical Quantum Computation, and Simulation Analysis

Less is More: Underlying Mechanism of Zn Electrode Long-Term Stability using Sodium L-Ascorbate as Electrolyte Additive.

Structured passivation layers and hydrated Zn2+ solvation structure strongly influence Zn depositions on Zn electrodes and then the cycle life and electrochemical performance of aqueous zinc ion batteries. To achieve these, the electrolyte additive of sodium L-ascorbate (Ass) is introduced into aqueous zinc sulfate (ZnSO4, ZS) electrolyte solutions. Combined experimental characterizations with theoretical calculations, the unique passivation layers with vertical arrayed micro-nano structure are clearly observed, as well as the hydrated Zn2+ solvation structure is changed by replacing two ligand water molecules with As-, thus regulating the wettability and interfacial electric field intensity of Zn surfaces, facilitating rapid ionic diffusions within electrolytes and electrodes together with the inhibited side reactions and uniform depositions of Zn2+. When tested in Zn||Zn symmetric cell, the electrolyte containing Ass is extraordinarily stably operated for the long time ≈3700h at both 1mAcm-2 and 1mAhcm-2. In Zn||MnO2 full coin cells, the energy density can still maintain as high as ≈184Whkg-1 at the power density high up to 2kWkg-1, as well as the capacity retention can reach up to 80.5% even after 1000 cycles at 2Ag-1, which are substantially superior to the control cells.

Synergistic Li6PS5Cl@Li3OCl composite electrolyte for high-performance all-solid-state lithium batteries

Li6PS5Cl is a highly wanted sulfide-solid-electrolyte (SSE) for developing all-solid-state lithium batteries, due to its high ionic conductivity, good processability and abundant compositional elements. However, its cyclability is poor because of harmful side reactions at the Li6PS5Cl/Li interface and growth of lithium dendrites inside Li6PS5Cl phase. Herein, we report a simple interface-engineering remedy to boost the electrochemical performance of Li6PS5Cl, by coating its surface with a Li-compatible electrolyte Li3OCl having low electronic conductivity. The obtained Li6PS5Cl@Li3OCl core@shell structure exhibits a synergistic effect. Consequently, compared with the bare Li6PS5Cl, this composite electrolyte exhibits great performance improvements: 1) In Li|electrolyte|Li symmetric cells, the critical current density at 30 °C gets increased from 0.6 mA cm−2 to 1.6 mA cm−2, and the lifetime gets prolonged from 320 h to 1400 h at the cycling current of 0.2 mA cm−2 or from 10 h to 900 h at the cycling current of 0.5 mA cm−2; 2) In Li|electrolyte|NCM721 full cells running at 30 °C, the cycling capacity at 0.2 C (or 0.5 C) gets enhanced by 20% (or from unfeasible to be feasible) for 100 cycles and the rate capability reaches up to 2 C from 0.2 C; and in full cells running at 60 °C, the cycling capacity is increased by 7% at 0.2 C and the rate capability is enhanced to 3.0 C from 0.5 C. The experimental studies and theoretical computations show that the performance enhancements are due to the confined electron penetration and suppressed lithium dendrites growth at the Li6PS5Cl@Li3OCl interface.